Sharif Digital Repository

Capillary pressure is one of the most important parameters for reservoir engineering studies. Although different experimental methods are devised to measure capillary pressure, these methods do not represent the physics of fluid flow, which happens at reservoir conditions. Thus, it is attempted to extract the capillary pressure from spontaneous imbibition data, the common mechanism of oil production in water wet porous media. In this work, a new approach is developed to obtain the imbibition capillary pressure curve by using spontaneous water imbibition data in oil-water-rock systems. Comparison of calculated imbibition capillary pressure curves by the new approach with experimental values... 

In this work a glass micromodel which its grains and pores are non-uniform in size shape and distribution is considered as porous medium. A two-dimensional random network modė, of micromodel with non-uniform pores has been constructed. The non-uniformity of porous model is achieved by assigning parametric distribution functions to pores throat and pores length, which was measured using image analysis technique. Statically derived expressions have been used for prediction of macroscopic properties of porous model including: dispersion coefficients, permeability-porosity ratio and capillary pressure. The results confirmed that predicted transport properties are in good agreement with the... 

Commonly, capillary pressure-saturation-relative permeability (Pc-S-Kr) relationships are obtained by means of laboratory experiments carried out on soil samples that are up to 10-12 cm long. In obtaining these relationships, it is implicitly assumed that the soil sample is homogeneous. However, it is well known that even at such scales, some micro-heterogeneities may exist. These heterogeneous regions will have distinct multiphase flow properties and will affect saturation and distribution of wetting and non-wetting phases within the soil sample. This, in turn, may affect the measured two-phase flow relationships. In the present work, numerical simulations have been carried out to... 

In this paper, results of DNAPL spreading experiments carried out in a geocentrifuge are analysed. The experiments are performed in the GeoDelft geocentrifuge. The experiments investigate the intrusion of a known amount of PCE into a water-saturated soil sample. They are carried out under 12, 15, and 30g conditions. The objectives of these experiments were to assess the potential of geocentrifuge tests for the study of environmental problems, to investigate the effect of acceleration on the spreading of DNAPL, and to determine whether capillary pressure-saturation (Pc-S) curves of soils measured in a geocentrifuge are applicable under 1g conditions. In the present paper, numerical simulation... 

In theories of multiphase flow through porous media, capillary pressure-saturation and relative permeability-saturation curves are assumed to be intrinsic properties of the medium. Moreover, relative permeability is assumed to be a scalar property. However, numerous theoretical and experimental works have shown that these basic assumptions may not be valid. For example, relative permeability is known to be affected by the flow velocity (or pressure gradient) at which the measurements are carried out. In this article, it is suggested that the nonuniqueness of capillary pressure-relative permeability-saturation relationships is due to the presence of microheterogeneities within a laboratory... 

Computational simulations of two-phase flow in porous media are used to investigate the feasibility of replacing a porous medium containing heterogeneities with an equivalent homogeneous medium. Simulations are performed for the case of infiltration of a dense nonaqueous phase liquid (DNAPL) in a water-saturated, heterogeneous porous medium. For two specific porous media, with periodic and rather simple heterogeneity patterns, the existence of a representative elementary volume (REV) is studied. Upscaled intrinsic permeabilities and upscaled nonlinear constitutive relationships for two-phase flow systems are numerically calculated and the effects of heterogeneities are evaluated. Upscaled... 

Most reservoirs in Iran are heterogeneous fractured carbonate reservoirs. Heterogeneity causes an earlier breakthrough and an unstable front which leads to a lower recovery. A series of experiments were conducted whereby the distilled water displaced n-Decane in strongly oil-wet glass micro-models containing a single fracture. Experimental data from image analysis of immiscible displacement processes are used to modify the Buckley-Leverett and fractional flow equations by a heterogeneity factor. It is shown that the heterogeneity factor in the modified equations can be expressed as a function of fracture length and orientation  

Capillary continuity between adjacent matrix blocks through formation of liquid bridge controls the recovery factor of gravity drainage process in fractured reservoirs. However, stability of liquid bridges as well as related capillary pressure in horizontal rough fractures is not well discussed in the available literature. In this work, new models of rough-walled fracture are developed and the role of roughness size and frequency on formation of liquid bridge and fracture capillary pressure are investigated. The Young-Laplace equation is numerically solved to characterize the liquid bridge formed in the proposed models of rough fractures. Critical fracture aperture for a range of liquid... 

Profile analysis tensiometry (PAT) is presently the most frequently used technique for measuring surface tensions of liquids. The basis of this methodology is however an equilibrium force balance as given by the Gauss-Laplace equation. Therefore, its application under dynamic conditions, i.e. for growing drops or bubbles, is questionable. We discuss the limits of the applicability of PAT under dynamic conditions by using a growing drop configuration equipped with a high speed video camera. The systems studied are the water/air and water/hexane interface. The obtained "dynamic" drop profiles are analyzed by fitting the classical Gauss-Laplace equation. The results are additionally compared... 

Spontaneous imbibition of water into the matrix is the most important mechanism for oil recovery in water wet fractured porous media. If the water is in contact with matrix and it is not flowing, the process is called static imbibition. The effect of rock and fluid properties, and boundary conditions on static imbibition are studied and formulated for scaling of the laboratory data to the reservoir scale. In reality, there is a continuous flow in a fracture; incorporating the effect of fracture flow into the scaling formulations is an unresolved issue in the modeling of the capillary imbibition recovery from the matrix. In this article, a new mathematical equation is developed to scale...